From a practical viewpoint, throwing birthday parties is a waste of energy and resources.In Triple Zero, Fi mentioned having never had a birthday celebration (though this would be impractical for clones, as so many of them share the same birthdate).

I would assume gifts may still happen, but I wouldn't expect a Mando to throw the kind of parties we see today.However, for the last birthday party I went to, we all went paintballing. Such an activity could be incredibly useful for Mandalorians, as it is a semi-harmless activity that can help hone some (but not nearly all) of their combat skills.

I'd imagine it'd be an affair for skraan'ikase possibly, given what's seen in I believe 501st. The scene where they have a "festival" type thing and Ny makes Kal cookies and shit. If you had the time to spend on such a thing. Like I guess if it fell around a time when someone returned back to the main yaim and we weren't running off back to war or something. They're not constantly out warring, after all.